This invention relates to electronic identification systems. The invention more particularly relates to radio frequency (RF) waveguides associated with spacers, carriers and containers for a plurality of items to be identified and for use with such systems. The invention also relates to an arrangement of items to be identified electronically and associated methods.
Electronic identification systems including an interrogator or reader and a plurality of transponders are well known in the art. In use, the interrogator transmits an RF energizing or interrogation signal towards the transponders to be identified and read. The transponder may utilize the energy in the energizing signal to power local circuits forming part of the transponder. The transponders then respond to the signal by transmitting a response signal including an identification code to the interrogate. The interrogator receives the response signal and reads the identification code. The code read is utilized to identify the transponder and an item or container on which it is mounted.
When the system is used with stacked or otherwise arranged item, the items may form an RF barrier between the interrogator and transponders mounted on the items or other carriers therefor. For example, in one application, crates for carrying containers (cans or bottles) holding a liquid such as a soft drink may each also carry a transponder forming part of the identification system. If these crates are stacked on one another, the containers form an RF barrier through which the energizing signal cannot propagate to energize or interrogate transponders in or on the other side of the barrier. The liquid reflects or absorbs the energy and the metal cans would reflect the energy.
Accordingly, it is an object of the present invention to provide a spacer, an arrangement of items and associated methods with which the applicant believes the aforementioned disadvantages may at least be alleviated.
According to the invention there is provided a spacer for goods or items including a waveguide for radio frequency waves. The spacer may include a body or in which the waveguide is mounted.
The body may include a carrier for goods such as a pallet. Alternatively, the body may include a container for goods. The container may be a crate.
The waveguide may be a planar waveguide having a characteristic impedance and including spaced first and second walls. The waveguide may comprise an antenna, preferably a slot antenna having an antenna impedance defined by the walls and the characteristic impedance of the waveguide preferably approaches the antenna impedance. This may be achieved by filling the waveguide with a suitable dielectric, such as oil, so that there is better impedance matching than would be the case between the antenna and an air filled waveguide, for example.
However, in preferred embodiments impedance matching means may be provided in the waveguide immediately adjacent the slot antenna. Such impedance matching means may include a quarter wavelength transformer comprising a dielectric material having a suitable relative permittivity. Normally such a material will be a resinous or plastic material. The rest of the waveguide may then be air filled.
A transponder of a radio frequency (RF) electronic identification system may be provided in the waveguide or in a further slot suitably dimensioned and positioned in one of said walls.
The first of said walls may include a peripheral transverse lip formation.
The second of said walls may also include a peripheral transverse lip formation extending away from the lip formation of the first wall, and the slot antenna may be defined between the lip formations.
In the case of a container, the waveguide may be provided in a bottom region of the container alternatively in a top region thereof.
A plastic body of the container may be permanently mounted between the lip formation of the first wall or the lip formation of the second wall. In other embodiments the plastic body may be removably receivable in the lip formation, so that the waveguide actually serves as a carrier or lid for the container.
Also included within the scope of the present invention is an arrangement of separate items, each of at least some of the items including a transponder of a radio frequency identification system, the arrangement including at least one waveguide extending at least partially through the arrangement to guide radio frequency energy between the transponders and a reader of the system. The reader may be located externally of the arrangement.
The items may be arranged in an array having parallel rows and columns.
Yet further included within the scope of the present invention is a method of arranging a plurality of items each including a transponder of a radio frequency electronic identification system, the method including the steps of:
arranging the items in an arrangement; and
forming a waveguide for radio frequency energy extending through at least part of the arrangement, to guide radio frequency energy between at least some of the transponders and a reader of the system.
Yet further including within the scope of the present invention is a method of identifying a plurality of items each including a transponder of a radio frequency electronic identification system also including a reader for the transponders, the method including the steps of:
arranging the items in an arrangement;
causing a signal transmitted by the reader to be guided by a waveguide to at least some of the transponders; and
causing response signals from the transponder to be guided towards the reader via the waveguide.